Comparison of MS trials baseline characteristics

Comparison of MS trials baseline characteristics

Background

The advent of therapies in MS has revolutionized its management. Several treatment options are now available to people with MS. As a consequence, it may become difficult to determine which one is best for a given patient. To make this decision, clear and objective comparisons of treatment characteristics are required. Such comparisons, to be reliable, would require the absence or at least the control of any confounding factor (such as medical history or age of the patient) that may bias the interpretation of clinical benefits or side effects. Patient characteristics at baseline (i.e. prior to treatment) are important confounding factors.

Data display

The below interactive parallel coordinates visualization presents the group-level baseline characteristics of 33 phase III or phase IV randomized controlled clinical trials in RRMS patients. The data were gathered from the articles presenting the main results of each trial respectively. This interactive plot allows you to compare baseline characteristics between trials. Select up to four trial names to enable the comparison. Mouse over the points and/or lines to reveal the specific trial/group values.

Note: In case of missing data (e.g. FREEDOMS II or PRISMS), the segmented line is interrupted but the points on the following axes (if any) are displayed.

One should not expect patient populations involved in various trials to be strictly identical. However, it is important to get a sense of how different these groups of patients are at baseline (i.e., before any treatment is taken), before conducting any between-trial comparisons.

Looking across all studies, the typical group of RRMS patients at baseline would have the following characteristics:

~70% women

patients of 36 years of age,

having experienced ~1.5 relapses during the year before entry in the study,

with 1st symptoms of MS having appeared approximately 7 years ago,

a disability (EDSS) score of 2.5,

the brain images revealing 2 gadolinium-enhanced lesions, a T2 lesion volume of about 9 cm3, and a brain volume of 1500 cm3.

Looking at the range of values for each axis respectively, we notice that most values are concentrated in only a small portion of the total range, which gives us the possibility to clearly identify the "outlying" groups or trials, such as IFNB-Mitox or GLANCE.

Further digging is possible. For instance, let's focus on AFFIRM and CLARITY trials. Differences can be noticed between these trials concerning disease duration (MSdur), patient disability (EDSS) and Gd-enhancing lesion characteristics at baseline. Such differences would have to be accounted for when comparing the outcomes of these two trials.

Parallel coordinates are similar in appearance to line charts, but their interpretations are substantially different. In line charts, lines are predominantly used to encode time-series; hence, slopes are key piece of information to extract from these charts. In parallel coordinates, slopes are not meaningful since lines connect series of values, each corresponding with a different variable, using its own range and unit. This is the reason why points were added to the above plot in order to emphasize the values observed on each axis respectively. On the other hand, line chart are 2D plots (x and y), where parallel coordinates are p-dimensional plots (with p, the number of coordinates or variables). The strength of interactive parallel coordinates resides in their ability to bring meaningful multivariate patterns and comparisons to light. Parallel coordinates convey a lot of information in a single plot. It is recommended to start looking at the big picture first, and then drill down to the specific values of each variable (vertical axis) and each profile (line path), thanks to the hovering and clicking options offered by this interactive chart.